Download or read book The Universality of Transitional Flow Behavior in Entangled Polymer Solutions written by Amy Philips and published by . This book was released on 2006 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Understanding the fast flow behavior of polymers remains a fundamental problem in polymer rheology. The objective is to determine a microscopic picture that relates the structure of a polymer in a given flow condition to the state of chain orientation. Recent work based on 1,4 polybutadiene solutions has found experimental differences in the state of chain entanglement between two different modes of imposing polymer flow, the conventional rate-controlled mode versus the stress-controlled mode. This work examines the universality of the yield-like entanglement/disentanglement flow transition and its characteristic features. A wide variety of polymer solutions with varying degrees of chain entanglement, polydispersity, solvent, and temperature, are investigated. All these different solutions share the same characteristic as found originally in the polybutadiene solution, to the extent that the measured shear rate grows considerably over a narrow range of the imposed shear stress indicating a high level of chain disentanglement. However, the rheology results indicate an apparent continuity in the steady state flow curves obtained with both controlled rate and controlled shear stress. The challenging experimental problem of edge instability/fracture during the flow transition is minimized with various techniques but it remains a formidable obstacle. The limitations of using rheological measurements to describe the nonlinear flow behavior of entangled polymers have not been overcome in this project."--abstract.
Download or read book Nonlinear Polymer Rheology written by Shi-Qing Wang and published by John Wiley & Sons. This book was released on 2018-02-06 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: Integrating latest research results and characterization techniques, this book helps readers understand and apply fundamental principles in nonlinear polymer rheology. The author connects the basic theoretical framework with practical polymer processing, which aids practicing scientists and engineers to go beyond the existing knowledge and explore new applications. Although it is not written as a textbook, the content can be used in an upper undergraduate and first year graduate course on polymer rheology. • Describes the emerging phenomena and associated conceptual understanding in the field of nonlinear polymer rheology • Incorporates details on latest experimental discoveries and provides new methodology for research in polymer rheology • Integrates latest research results and new characterization techniques like particle tracking velocimetric method • Focuses on the issues concerning the conceptual and phenomenological foundations for polymer rheology • Has a companion website for readers to access with videos complementing the content within several chapters
Download or read book How Do Entangled Polymer Liquids Flow written by Sham S. Ravindranath and published by . This book was released on 2010 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the nonlinear flow behavior of entangled polymer liquids has immense significance because of its direct relevance and usefulness in predicting behavior of these liquids during processing. In startup shear, it is well known that shear stress overshoot emerges when the rate of shearing is higher than the inverse of overall chain relaxation time [Tau]. For solutions with the number of entanglements per chain Z [greater than or equal to] 25, we have revealed using PTV that the shear field becomes inhomogeneous across the gap after the stress overshoot. For solutions with Z [greater than or equal to] 40, the shear stratification persists even in steady state, indicating that different states of chain entanglement are possible corresponding to the same shear stress. The number of entanglements per chain, Weissenberg number, the shear history, the type of solvent used, and polydispersity of the system are some of the control parameters that can strongly affect the observed nonlinearity. PTV observations of step strain experiments revealed a great deal of information about the physics of polymer flow. Contrary to the common perception that the entanglement network would be strong enough so that it would not collapse after a large step strain, macroscopic motions in the sample interior were observed after shear cessation at strains [greater than or equal to] 135%. The collapse of the entanglement network after shear cessation suggested that the entanglement network is a fragile system of finite cohesive strength and cannot escape structural failure. In other words, the network disintegrates when an elastic retractive force greater than the cohesive strength of the network is built due to deformation. PTV technique also revealed the coexistence of multiple shear rates under large amplitude oscillatory shear (LAOS) across the sample thickness in entangled solutions with Z [greater than or equal to] 25. In the Lissajous plots (shear stress vs. shear strain), distortion of an ellipse begins to appear when the nonlinear velocity profile is first noticed. These observations are again contrary to the conventional perception that the system undergoing LAOS will experience homogeneous shear in each cycle so that material functions can be introduced to analyze the nonlinear dependence of these functions on the amplitude and frequency. The above mentioned experimental observations in simple shear as well as in uniaxial elongation of entangled polymers has helped us to recognize that three forces (intermolecular locking force, retractive force and entanglement cohesive force) play important roles during response of a deformed entanglement network. The new theoretical considerations have further helped us to discover the striking scaling features associated with stress overshoot in well entangled polymer solutions and melts.
Download or read book Rheology and Turbulent Flow Behaviour of Polymer Solutions written by Kam Chiu Tam and published by . This book was released on 1990 with total page 898 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of Rheology written by and published by . This book was released on 2008 with total page 650 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes abstracts from the Journal of the Society of Rheology, Japan.
Download or read book Nonlinear Rheolgy Of Entangled Polymers written by Keesha Hayes and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Doi-Edwards (D-E) molecular, viscoelastic theory for entangled polymers is used as the framework for an experimental study of flow anomalies in well-characterized polymer solutions and melts, spanning a wide range of entanglement densities. Results of linear viscoelastic and nonlinear rheology experiments - steady and step shear were compared to existing theory. Unlike weakly and moderately entangled polymers (N/Ne [LESS-THAN OR EQUAL TO]11), the step-shear damping function, h ([gamma]) = G (t, [gamma])/ G (t, [gamma][RIGHTWARDS ARROW]0), for polymers with high entanglement densities is more strain softening than the Doi-Edwards prediction, hD-E ([gamma]). Two likely causes of this deviation, commonly called type C Damping, are interfacial slip and shear banding. To isolate the mechanism(s) responsible for the discrepancy, we combine macroscopic techniques (rheometry) with direct visualization (confocal microscopy and particle image velocimetry) during steady shear flow. In the latter case, this high resolution measurement technique allows us to construct the velocity profile in narrow-gap, planar-Couette shear flow. Importantly, even for shear rates well into the non-Newtonian shear-rate regime, where the unmodified D-E theory predicts shear banding, all the shear profiles are found to be linear. There is strong evidence of interfacial slip, which can be characterized and compared to slip theories for entangled polymers. To remove/ weaken the role of slip, the original confocal set-up was modified to allow both a transient shear and large-gap study. These results were compared with qualitative expectations from transient constitutive curves: [sigma] ([gamma] ) vs. [gamma] , measured at similar times in mechanical rheometry experiments. During start-up of steady shear flow, rheometry measurements show a maximum in [sigma] ([gamma] ) vs. [gamma] at times prior to steady state. To determine whether this transient, non-monotonic stress growth leads to transient shear banding, we characterized the velocity profile as a function of time. Surprisingly, these measurements again yield decidedly linear profiles that vary little with time, indicating that there is some feature of the shear flow that stabilizes it against banding. Finally, step shear experiments with entangled star-branched polymer solutions reveal that the damping function is universal but different from hD-E ([gamma]). And, linear and nonlinear rheology of unentangled stars indicates that their flow behavior follows Rouse model predictions. . . . .
Download or read book The Behavior of Polymer Solutions in Extensional Flow Developed by Drop Elongation written by Thomas Anthony Wahlheim and published by . This book was released on 1982 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Flow Behavior of Dilute Polymer Solutions written by Richard Bruce Reznik and published by . This book was released on 19?? with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transient Shear Flow Behavior of Polymer Solutions written by Jerry Kenneth Okeson and published by . This book was released on 1975 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Toms Phenomenon written by Preetinder Singh Virk and published by . This book was released on 1966 with total page 906 pages. Available in PDF, EPUB and Kindle. Book excerpt: Drag reduction caused by dilute, distilled water solutions of five polyethylene oxides, molecular weights from 80,000 to 6,000,000, in turbulent pipe flow was studied experimentally in 0.292 cm and 3.21 cm ID pipes. It was found that: The onset of drag reduction occurs at a well-defined wall shear stress related to the random coiling effective diameter of the polymer by the Onset Hypothesis. Laminar to turbulent transition is not, in general, delayed. The extent of drag reduction induced by a homologous series of polymers in a given pipe is a universal function of concentration, uniquely related to flow rate and molecular weight. The maximum drag reduction possible is limited by a universal asymptote that is independent of polymer and pipe diameter. In polymer solution, both the stagnation pressure attained with Pitot tubes and the heat transfer from cylinders in cross flow are drastically different from Newtonian; in general, both are lower. (Author).
Download or read book The Behavior of Dilute Polymer Solutions written by Jenq Jang Ou and published by . This book was released on 1981 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polymer Solutions written by Iwao Teraoka and published by John Wiley & Sons. This book was released on 2004-04-07 with total page 355 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer Solutions: An Introduction to Physical Properties offers a fresh, inclusive approach to teaching the fundamentals of physical polymer science. Students, instructors, and professionals in polymer chemistry, analytical chemistry, organic chemistry, engineering, materials, and textiles will find Iwao Teraoka’s text at once accessible and highly detailed in its treatment of the properties of polymers in the solution phase. Teraoka’s purpose in writing Polymer Solutions is twofold: to familiarize the advanced undergraduate and beginning graduate student with basic concepts, theories, models, and experimental techniques for polymer solutions; and to provide a reference for researchers working in the area of polymer solutions as well as those in charge of chromatographic characterization of polymers. The author’s incorporation of recent advances in the instrumentation of size-exclusion chromatography, the method by which polymers are analyzed, renders the text particularly topical. Subjects discussed include: Real, ideal, Gaussian, semirigid, and branched polymer chains Polymer solutions and thermodynamics Static light scattering of a polymer solution Dynamic light scattering and diffusion of polymers Dynamics of dilute and semidilute polymer solutions Study questions at the end of each chapter not only provide students with the opportunity to test their understanding, but also introduce topics relevant to polymer solutions not included in the main text. With over 250 geometrical model diagrams, Polymer Solutions is a necessary reference for students and for scientists pursuing a broader understanding of polymers.
Download or read book The Behavior of Polymer Solutions in Non uniform Flows written by Yoram Cohen and published by . This book was released on 1981 with total page 882 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Elongational Flows written by Chris J. S. Petrie and published by Pitman Publishing. This book was released on 1979 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Triggered Laminar to turbulent Transition in Pipe Flows of Dilute Polymer Solutions written by Makoto Ohara and published by . This book was released on 1968 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental and Modeling Studies of Extensional and Shear Flow Behavior of Polymer Solutions written by Vishal Gauri and published by . This book was released on 1996 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Steady state One dimensional Pressure driven Pipe Flow of Polymer Solutions with Concentration stress Coupling written by Yassine Dhane and published by . This book was released on 2016 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new approach to model the flow of polymer solutions is investigated. The flow behavior of these materials has been under investigation for decades without reaching a consistent explanation of the observed phenomena such as shear banding in shear flow and the spurt phenomena in pressure-driven pipe. In this investigation, we explore the coupling of the mass transport and the viscoelastic dynamics and its influence on the flow of polymer solutions in pipes. We implement a predictive constitutive model for polymer solutions that reproduces observed flow behaviors using scaling arguments to estimate material properties from a minimal number of measured quantities. The inherent existence of multiple solutions to the model's system of equations allows for the prediction of sudden increases of flow rate in a pressure-driven channel flow is reported due to a stress-induced depletion layer at the pipe wall of the size of the correlation length of the solution. This investigation bridges the gap between theoretical studies that focus on the interfacial physics and those that focus on the bulk flows to explain the spurt phenomena of polymer solutions.
